Rising Sea Levels and Bigger Storms May Cause Major Flooding on the East Coast

Rising seas and bigger storms are threatening the coast of the United States. Now, scientists have taken a closer look at how predicted storms and sea level rise might interact to produce spikes in flooding.

"When you look at hazards separately, it's bad enough, but when you consider the joint effects of two hazards together, you can get some surprises," said Radley Horton, a climate scientist and co-author of the new study, in a news release. "Sometimes, one plus one can equal three."

Over the past century, the East Coast has seen sea-level rise far above and beyond the 8-inch global average. In fact, there's been up to a foot in the Mid-Atlantic and Northeast, including New York City. Sinking land and currents that chronically drive water coastward have worsened matters. In fact, most projections call for a further 2- to 4-foot rise by 2100.

At the same time, separate studies suggest that the intensity of the biggest storms generated in the North Atlantic may increase, because warmer waters contain more energy. Projections of this phenomenon are somewhat less certain, but scientists are taking them with increasing seriousness.

In this new study, the researchers made two projections for the 21^st century. One is based on if the world greatly reduces emissions of greenhouse gases, and one is if the current trajectory continues. Even the reduced-emissions calculations, though, suggest a 4- to 75-fold increase in the flood index; in other words, the combined heights and durations of expected floods are expected to increase across five locations. If a business as usual scenario occurs, then the flood index could go up 35 to 350 times.

So what cities would be in trouble? The researchers examined Atlantic City, NJ; Charlestone, SC; Key West, Fla; Pensacola, Fla; and Galveston, TX. All of those locations would experience increased flood threats.

The findings are published in the journal Nature Climate Change.

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